The extra £8bn that the Tories have pledged, £37bn extra from Labour or £6bn a year for health and social care by the Liberal Democrats would all leave the NHS short of money, it said. In their election manifestos the parties have pledged to give the NHS sums smaller than those recommended by the Office for Budget Responsibility (OBR), the Lords select committee on long-term NHS and social care sustainability as well as NHS organisations such as those representing hospital trusts.

“None of the political parties’ promises matches even the lowest projections of what funding should be. Spending as a proportion of GDP looks set to fall slightly whichever party forms the next government, unless additional funds can be found,” said Prof John Appleby, chief economist and director of research at Nuffield Trust.

Its analysis of the parties’ pledges found that the NHS budget in England would reach £135.3bn in 2022-23 under Labour’s proposals, £132.2bn with the Liberal Democrats and £131.7bn under the Tories.

But the thinktank said NHS spending would be £155bn that year if ministers heeded the OBR’s recommendation that the service be given budget increases of 4% a year above inflation to help it cope with population increases, patient demand and medical advances. Growing the NHS in line with rising GDP would see it receive £137bn that year, while giving it enough money to cope with inflation would result in its budget being £141bn

Labour and the Tories declined to respond directly to the thinktank’s findings.

Jonathan Ashworth, the shadow health secretary, said: “The choice is clear in this election: substantial investment in the NHS with Labour to reduce waiting lists and give patients the very best care or more of the same under the Tories – a big funding squeeze and deteriorating standards of care.”

A Conservative spokesman said: “We disagree with this analysis, as the IFS [Institute for Fiscal Studies] has said that the Conservatives have matched Labour’s NHS spending commitments. But in truth only Theresa May will grow the economy and actually deliver her promises. Because, in contrast to the nonsensical Jeremy Corbyn, only she can get Brexit right, which underpins everything else, including NHS funding.”